Various equipment and techniques have been devised for rotating a downhole tubular member, such as a section or joint of casing or drill pipe. Those skilled in hydrocarbon recovery operations appreciate that various anticipated or unexpected problems require either the makeup of tubulars downhole to provide a fluid-tight threaded connection, the breaking out of tubulars to structurally separate one tubular section from another tubular section, or the desired rotation of a tubular section which does not extend to the surface of the well. Tools and techniques which can reliably perform these operations in a cost efficient manner having long been desired by the hydrocarbon recovery service industry.
To provide a downhole breakout operation, it is conventional to apply left hand torque to the tubular string from the surface, then jar or shock the tubular string in the vicinity of the connection to be broken apart. The jarring or shocking action may be imparted by a jarring tool, or by a downhole explosive device set off near the connection to be broken. This technique, while having the benefit of relatively low cost, is not highly reliable. Any threaded connection above that to be separated is inherently subjected to the same or a higher left hand torque, and thus these upper connections may unintentionally separate before the connection to be broken apart separates. To provide the desired high reliability to break out the downhole tubular connection, back-off tools have been developed which are lowered downhole on a work string to straddle and unscrew the connection to be separated. A prior art casing back-off tool offered by Tri-State Oil Tools, Inc. includes an upper member for anchoring to the casing above the connection to be broken, a lower member for anchoring to the casing below the connection to be broken, and an intermediate back-off tool portion. Right hand threads are used throughout the breakout tool, and hydraulic pressure applied from the surface causes axial and rotational movement of a hydraulically responsive piston, which then rotates the upper anchoring member and thus the casing interconnected therewith, breaking apart the threaded connection. High breakout forces are typically required to "break" the connection, and thereafter relatively low forces are required to repeatedly stroke the piston to completely separate the threaded casing connection.
In another situation, a casing may become stuck in the borehole, and the drilling operator may separate and remove the upper section of casing, while leaving the lower stuck casing downhole. The drilling operator thereafter need rotate only the stuck lower casing to free it from the borehole. In this case, a hydraulically operated reversing tool may be positioned downhole on a work string above the stuck casing, and may be activated to apply a left-hand torque to the stuck lower casing to hopefully unstick the casing from the wellbore. A Tri-State reversing tool includes an upper member for securing the tool within the wellbore, and a lower reversing portion which connects with the upper end of the stuck casing. Hydraulic fluid axially moves and rotates a driving piston, which transmits the desired reversing torque to the downhole tubular. The reversing tool includes an exterior spline to keep applied torque in the stuck casing, and generates left hand torque to unscrew the "fish" or stuck tubular.
While back-off tools and reversing tools have long been used in the oil recovery service industry, a practical downhole tool is not being used for makeup of a downhole tubular connection. Particular problems arise with respect to makeup of a downhole connection, which problems are not encountered when breaking out a connection or when utilizing a reversing tool to unstick a downhole tubular section. For example, when breaking out a tubular connection, damage to the connection threads is not envisioned, and there are no problems concerning alignment of the tubulars since the connection is already made up. Also, a relatively high torque must be initially applied to break out the connection, and thereafter only a comparably low torque need be applied to complete the break-out operation. By comparison, damage to the threads of the connection is a significant concern during a downhole makeup operation. Also, axial alignment of the tubulars must be performed prior to a downhole makeup operation, and a relatively low initial torque and a high final torque are required when making up the downhole connection.
The hydrocarbon recovery service industry has accordingly continued to accept the substantial risks associated with making up downhole tubular connections by trying to "stab-in" the upper tubular threads to the lower tubular threads, and then rotating the upper tubular from the surface to complete the makeup operation. Those skilled in the art have long recognized that the threaded ends of the tubular connections become damaged during this stabbing operation, since the tubulars to be connected are seldom centrally aligned within the borehole. Even if the stabbing connection is successfully made, it is difficult to estimate the torque which is actually applied to the downhole connection during the makeup operation, since a significant difference exists between the torque applied to the tubular at the surface compared to the torque applied to the downhole connection, particularly if the tubular is within a deviated well. The technique of making up a downhole connection by turning the tubular at the surface is thus at best reliable only if there is little torque resistance in the tubular string extending to the surface. Since the wellbore walls are typically engaged by the tubular string and add substantial torque resistance, the desired downhole torque cannot be assumed to be the torque applied to the tubular string at the surface.
In many instances, the stabbing operation damages the threads, particularly when tubulars employing premium threads having metal-to-metal seals adjacent end surfaces of the tubulars are utilized. The upper tubular string then is typically removed from the wellbore, and a downhole tool inserted to cutoff the lower tubular section below the damaged threads. The lower end of the upper tubular string section similarly may be modified so that a seal and latch assembly or casing patch device may subsequently be utilized to form a seal between the adjoining unthreaded tubular ends within the wellbore. The casing patch device thus stabs over the cutoff tubular, and relies on the sealing medium of the patch, which may be lead, to seal the casing joints together. Other patches utilize metal-to-metal seals to offer more reliability than elastomeric materials or lead as a sealant, although these patches must have special clearances and surface finishes which often cannot be economically obtained throughout the life of the well. Special patch repair equipment and techniques have thus been devised to sealingly connect the downhole upper and lower tubular sections when the threaded ends have been removed from the tubulars to be connected. These patch operations are not favored by those skilled in the industry, however, and significant risks are encountered when utilizing this patch technique, particularly when the tubular string is thereafter subjected to repeated high pressure and de-pressuring operations. The patch thus may be unable to withstand the dynamic forces subsequently generated by casing movements and/or downhole temperature fluctuations.
Even if a tubular connection is made up downhole by applying torque to the upper tubular section at the surface, the threaded connection may not form the desired reliable seal when subjected to high pressure, due to damage of the threads during the stab-in or makeup operation. In other instances, pressure tests on the integrity of the downhole made up connection may indicate a successful makeup, but the connection thereafter may fail since excessive torque or an insufficient torque may have been applied during the makeup operation, resulting in failure after the made up connection has been in use for a period of time. Tubulars manufactured from special corrosion resistant material are often used to enhance the useful life of the recovery operation. Premium connections used in oil country tubular goods require the reasonably accurate monitoring of torque during the makeup operation if the integrity of the connection is to be guaranteed, and this goal is typically not obtained when rotating a tubular at the surface to complete the makeup operation.
The disadvantages of the prior art are overcome by the present invention. A downhole makeup tool and an improved method of making a reliable downhole threaded connection are hereinafter disclosed which overcome the disadvantages of the prior art. The downhole makeup tool and the technique of the present invention are thus able to reliably makeup a downhole threaded connection, thereby minimizing the risks associated with the recovery of hydrocarbons from a well.